The present invention relates to a liquid crystal display (LCD) panel and a manufacturing method thereof for use in optical displays, and more particularly, to an LCD panel and a manufacturing method thereof which has insulating layers for dividing a liquid crystal layer into multiple layers and supports for supporting the insulating layers.
A wide variety of liquid crystal displays have been developed as image display devices and cover a broad range of applications as a result of its lightweight and simple structure, similar to a plasma display panel or electroluminescent display. Moreover, the low drive voltage of such LCDs results in reduced power consumption.
Among currently used liquid crystal displays, simple-matrix and active-matrix types using a thin film transistor require at least one polarizer for light control because they employ twisted nematic (TN) or super twisted nematic (STN) liquid crystal. However, since a polarizer blocks over 50% of the light in the course of light polarization, the polarizer drastically reduces the light utilization efficiency of an image display device.
In order to obtain an image of an intended brightness in such a display, a background light source of high luminance must be adopted. Thus, liquid crystal displays are impractical for laptop wordprocessors or minicomputers using a dry cell or rechargeable battery due to their excessive power consumption which renders extended operation impossible.
Since general LCDs (including those using TN or STN liquid crystal) have a structure in which liquid crystal is filled between two glass plates, the distance between the two glass plates, that is, a cell gap which is a light controlling area, should be strictly controlled for the formation of a uniform image. However, given the present level of manufacturing technology for fabricating such glass plates, a large-screen LCD display cannot be realized.
Considering the above-discussed drawbacks, it becomes necessary to simplify the control of the cell gap by employing a single plate, and to counteract the negative effects on light utilization efficiency caused due to the polarizer.
According to the conventional technology, an LCD having no polarizer has also been developed. Such LCDs without polarizer include a cholesteric-nematic type liquid crystal which makes use of the phase transition effect and a dynamic scattering mode type liquid crystal which was an early development. The dynamic scattering mode LCD has a slow response and is relatively thick, which greatly impedes its application and ultimately restricts the scope of usage.
Another liquid crystal display without polarizer, and thus exhibiting better light efficiency, is a polymer-dispersed type. However, since over 50% of the volume of the polymer-dispersed liquid crystal is made up of light-transmitting polymer, dispersion should be performed effectively so as to enhance contrast and thereby improve clarity. For this purpose, the polymer-dispersed liquid crystal should be at least 20 .mu.m thick, which is a structural limitation.
An electric-field-effect LCD having a novel structure to overcome the diverse problems in the conventional displays is disclosed in U.S. patent application No. 08/058,712 by Nobuyuki Yamamura, hereby incorporated by reference. Subsequently, improvement applications were filed by the applicant as U.S. patent application Nos. 08/111,063, 08/058,712, 08/169,283, 08/155,258, 08/169,244, 08/170,940, and 08/169,243, which are hereby incorporated by reference.
Having a rapid driving speed and high light-utilization efficiency, the above liquid crystal displays are constructed so that a liquid crystal layer placed between opposing electrodes is separated by a plurality of insulating layers to be thereby divided into multiple layers. Here, a single glass plate is employed without a polarizer and a function layer for light control lies above the plate.
FIGS. 1, 2, 3 and 4 illustrate a liquid crystal display having a greatly improved structure with respect to that first proposed by Yamamura. Referring to FIGS. 1, 2 and 3, electric-field-effect liquid crystal layers 21 are located between opposing striped electrodes 11 and 12. Columnar supports 41 are placed within a pixel area of the liquid crystal area, and latticed supports 42 being discontinuous at regular intervals are located outside the pixel areas. The supports 41 and 42 are provided in liquid crystal layer 21. Insulating layers 22 divide the liquid crystal into their respective layers 21 and are secured by supports 41 and 42. Liquid crystal injection holes 30 are formed in the insulating layers corresponding to the portions where latticed supports 42 become discontinuous. Here, the thickness of respective liquid crystal layers 21 should be below 3 .mu.m, with the thickness of insulating layers being below 5 .mu.m. In the disclosure, Yamamura indicates that epoxy resin, or, as the case may be, a metal oxide and especially aluminum oxide, may be used for insulating layer 22. A manufacturing process for the above liquid crystal display has the following steps:
(a) An electrode made of conductive material is formed on an electrically insulating glass substrate; PA1 (b) An electrically insulating light-transmitting material, which cannot be dissolved by a predetermined solvent, is coated on the electrode so as to form an insulating layer; PA1 (c) A material which can be dissolved by the above predetermined solvent is coated on the insulating layer so as to form a dissolution layer; PA1 (d) Steps (b) and (c) are repeated for predetermined number of times so as to form a stack of insulating and dissolution layers; PA1 (e) An electrode made of a light-transmitting conductive material is formed on the stack of the insulating and dissolution layers; PA1 (f) First holes are vertically perforated through the stack formed from step (b) to step (d) at predetermined intervals, and the holes are filled with a light-hardening material so as to form vertical supports; PA1 (g) Injection holes are formed in the stack at predetermined intervals, and the solvent is fed therethrough to remove the dissolution layer formed during step (c); and PA1 (h) Liquid crystal is filled in the space from which the dissolution layer is removed, through the liquid crystal injection holes, and, finally, the holes are plugged.
In the above-described manufacturing method, the material for the dissolution layer for securing a space for liquid crystal to be filled is water-soluble PVA, and the material of the insulating layer is epoxy resin. Here, aluminum can be used for the water-soluble PVA and metal oxide can be used for the epoxy resin. However, in the method, the steps for forming the insulating layer and supports are very complicated, and other elements may be damaged during the etching step.
Particularly, when the dissolution layer is dissolved via the liquid crystal injection holes for injecting liquid crystal into a cavity formed by the dissolution of the dissolution layer, which are designed to be spaced apart from the supports, etching requires an excessively long time because the total area of the dissolution layer is about 200 times that of the liquid crystal injection holes. During etching, the shape of the liquid crystal injection holes tends to become deformed, and the deformed injection holes cause trouble in injecting liquid crystal.